Back-fire release for internal combustion engines



1934- w. L. MCGRATH 1,981,120

BACK FIRE RELEASE FOR INTERNAL COMBUSTION ENGINES Fil ed Oct. 31, 1931 nnllluflm 23, i @ffl I E INVENTOR j Ia/ me. mcrcvth/ Patented Nov. 20, 1934 BACK-FIRE muss roa mmu'ar.

conmus'rron mamas William n'nccmm Elmira, .N. 1;, a-lgnor to Eclipse Machine Company, Elmira,

notation of New York N. Y., a cor- Application October 31, 1931, Serial No. 572,249

llOlaims.

This invention relates to a back-fire release for internal combustion engines and more particularly a device for preventing damage to engine starting mechanism due to backward rotation of such engines. y

g It is well known that the actuation of an enginestarting mechanism when the engine is rotating backward causes heavy stresses to be developed which may cause failure of the parts subjected thereto. when controlling devices are employed for facilitating or institutingthe actuation of the starting mechanism, it therefore becomes important to automatically prevent such actuation during .backward rotation of the.

5 e e. Y

It is an object ,of this invention to provide a novel device for rendering the engine starting mechanism inoperative as a result of back-fire or backward rotation of the engine.

Another object of the invention is to provide such a device which retains the starting mechanism in its inoperative condition regardless "of the cessation of the back-firing or backward rotating condition. I

A further object is to provide such a device embodying manual means for again rendering the starting mechanism operative.

Further objects and advantages will become apparent to those skilled in this art from the following .description taken in connection with the accomp nyin drawing in which:

Fig. 1 is a semi- :1 showingof a preferred embodiment of the invention as used in conjunction with an ordinary starting relay circuit, the back-fire release device being sectioned on line 1-1 .of Pig. 3;

Fig.2isasimilarview of the deviceasused in conjunction withaknown form of automatic starting mechanism the parts of the back-fire release being shown in the positions which they assume as a result of back-fire; and

Fig. 3 is a cross section ofthe back-lire release ontheline33ofl"lg. 1.

mm. 1 of the drawing thereisillustrated an electrical" starting system for an internal combustion engine (not shown) including a battery 1groundedat2andconnectedbyale'ad3 to an electromagnetic starting switch indicated generally by the numeral 4. This starting switch 0 comprises a movable switch-member 5 adapted to bridge contacts 8 and 7, thus completing a circuit through lead 8 to the starting motor SM which is grounded at 9. The switch plunger 5 is adapted to be actuated by.a solenoid 11 which is embodied in a control circuit including a battery lead 12, manual switch 13, lead 14, backflre release device 15, lead 16 and ground lead 17, the arrangement being such that closureof the control circuit causes energization of solenoid 11 to close the starting circuit and energize the starting motor.

The back-lire releasing device indicated generally at 15 is mounted on the intake manifold 22 of the engine to be started, and comprises a casing 18 containing a metallic diaphragm 19 forming a closed chamber 21 whichis in communication with the intake manifold 22 of the engine as by means of a e 23 in an extension 24 of casing 18 which is threaded in an opening in said manifold." A pair of insulated binding posts 25 and 28 are mounted in the top of casing 18, the binding post 25 being connected to a stationary contact member 27; and binding post 26 being connected to a spring contact member 28 which is normally in engagement with contact 27. The outer end of spring contact28isarrangedtobearonapoa29 ofinsulating material which rests on the center of the diaphragm l9, and is retained in position by suitable means such as a pilot pin 30 traversing the contact member 28 and entering the post 29. The diaphragm is slightly dishedso as toform' a snap diaphragm which maintains its position as illustrated in either Pig. 1 or Fig. 2 until it is movedinto its other position by some extraneous force.

When the diaphragm 19 is in its lower position as illustrated in Fig. 1, the spring contact 28 is allowed to rest on the fixed contact 27, thus completing the circuit through the backflre release. When the diaphragm is raised to its upper position as shown in Fig. 2 by pressure within the intake manifold 22, the post 29 is arranged to move the spring contact 28 out' of engagement with the fixed contact 27 as there illustrated which position will be maintained until pressure is applied to the upper surface of the diaphragm to force it to its lower position. In Fig. 1, a plunger. 31 is provided for manually returning the diaphragm to its lower position in order to allow the contacts 27 and 28' to close. I

In Fig. 2 there is illustrated a second embodi- .ment of the invention in which the back-fire releasing device is used in conjunction with an automatic starting mechanism for causing the vice 55, lead 56 and lead 57. This circuit is similar to the control circuit illustrated in Fig. -1,

'but the lead 57 of solenoid 51 instead of being connected directly to the ground is grounded through the generator G driven by the internal combustion engine. It will thus be seen that when the engine starts, the solenoid 51 will be.

deenergized by reason of the counter E. M. F. of

the generator opposing the battery voltage. Theswitch 53 may therefore be left closed at all timeswhile the engine is running and hence may be also used as the ignition switch for the engme.

The back-fire release device 55 is similar in all respects to the back-fire release 15 except that the manual plunger 31 has been omitted. In place of this plunger, 9. push button 58 is provided which maybe located in a position convenient to the operator and which when depressed shunts out the back-fire release device 55 and causes actuation of solenoid 51 when the ignition switch 53 is closed. The consequent cranking of the engine causes a partial vacuum to be created in the intake manifold 22 whereby the diaphragm 19 is sucked down to its lower position, allowingthe contacts 27 and 28 to close, whereupon the automatic starting mechanism is again placed inoperative condition.

In the operation of the embodiment of the invention disclosed in Fig. 1, closure of the manual switch 13 causes actuation of solenoid 11 to close the starting switch and cause the engine to be cranked. If the engine starts successfully, the operator opens the switch 13 and the starting switch is thereupon returnedto normal position. If the engine should back-fire, however, pressure isimmediately built up in the intake manifold 22 by the backward rotation of the engine whereby the diaphragm 19 is moved to its upper position, breaking contacts 2'7 and 28 and rendering the solenoid 11 inoperative whereby engagement of the starter during backward rotation of the engine is prevented. when the backward rotation has ceased, the operator presses the plunger 31 to return the diaphragm 19 to its normal position whereupon switch 13 may be again closed and the starting operation repeated.

In the embodiment of the invention illustrated in Fig. 2, closure of the switch 53 by the operator closes the ignition circuit and also the control circuit through the solenoid 51 whereby the starting switch member. 45 is moved to closed position to cause the engine to be cranked.

If the engine starts properly, the counter E.

F. of generator G opposes the flow of battery current through the solenoid 51, thus deenergizing said solenoid and causing the starting switch tor, after the backward rotation has ceased to depress the push button 58, thus energizing solenoid ,51 and causing the cranking operation to be repeated. The consequent suction created in the intake manifold 22 causes the diaphragm 19 to return to its normal positionawhereupon the push button 58 may be released and the automatic starting mechanism will proceed to function in its usual manner.

Although but two embodiments of the invention have been shown and described in detail, it will be understood that other embodiments are possible and various changes may be made in the construction and arrangements of the parts and certain features thereof may be used without other features without departing from the spirit of the invention as defined in the claims appended hereto.

What is claimed is:-

1. In combination with an internal combustion engine, starting mechanism therefor including a starting motor, manually controllable means for actuating said starting motor, means responsive to backward rotation of the engine for rendering said actuating means inoperative, and manually controllable means for returning the actuating means-to operative condition.

2. In combination. with an internal combustion engine, starting mechanism therefor including a starting switch, manually controllable means including a control circuit for actuating said starting switch, means responsive to backward rotation of the engine for opening the control circuit, and manually controllable means for closing the control circuit.

3. In combination with an internal combus tion engine, starting mechanism therefor including a starting switch, manually controllable means including a control circuit for actuating said starting switch, a pair of contacts in said control circuit, means responsive to backward rotation of the engine for opening said contacts and manually controllable means for causing said contacts to be closed.. I

4. In combination with an internal combustion engine having a fuel intake system, starting mechanism therefor, means responsive to positive pressure higher than atmospheric pressure insaid intake system of the engine for preventing the operation of the starting mechanism and manually controllable means for rendering the starting mechanism operative.

5. In combination with an internal combustion engine having a fuel intake system, starting mechanism therefor including a starting switch,- means including a control circuit for closing said starting switch, means responsive to pressure in said intake system of the engine for opening said control circuit, and responsive to forward rotation of the engine to close said opening in the control circuit, and manually controllable means to institute forward rotation of the engine.

6. In combination with an internal combustion engine, automatic starting mechanism therefor including a starting switch, manually controllable means for automatically closing said switch in case of engine stall, means actuated by backward rotation of the engine for preventing automatic closure of the starting switch and 14 controllable means for automatically closing said switch in case of engine stall, means actuated by backward rotation of the engine for preventing automatic closure of the starting switch,

said preventing means being actuated by forof said control circuit, said preventing means being actuated by suction in the intake system to reestablish automatic actuation of the control circuit.

9. In combination with an internal combustion engine having a fuel intake system, starting mechanism therefor including a starting switch, manually controllable means for actuating said starting switch including a control circuit, means for automatically energizing said control circuit in case of engine stall, means actuated by pressure in said intake system of the internal combustion engine for preventing energization of said control circuit, said preventing means being actuated by suction in the intake system to reestablish automatic actuation of the control circult, and manual means independent of said preventing means for initiating the actuation of the starting mechanism.

10. In combination with an internal combustion engine having a fuel intake system, starting mechanism therefor including a starting switch, manually controllable means for actuating said starting switch including a control circuit, means for automatically energizing said control circuit in case of engine stall, a pair of contacts in said control circuit, a snap diaphragm for opening said contacts in response to pressure in the intake system of the internal combustion engine, and manual means for returning the contacts to closed position.

11. In combination with an internal combustion engine having a fuel intake system, starting mechanism therefor including a starting switch, manually controllable means for actuating'said starting switch including a control circuit, means for automatically energizing said control circuit in case of engine stall, a pair of contacts in said control circuit, a snap diaphragm for opening said contacts in response to pressure in said intake system of the internal combustion engine, and closing said contacts responsive to suction in said intake system, and manual means for initiating the operation of the starting mechanism when said contacts are open whereby the suction in the intake system serves to reclose said contacts and reestablish automatic operation of the starting mechanism.

WILLIAM L. McGRATH. 

